Documenting behavior of returning a 0-length array for formats,

channels, rates queries for analog devices.

Bug: 22729461
Change-Id: I3cb1d586f6264e3627cbb0261a3b2c74ca51cf6b

media/java/android/media/AudioDeviceInfo.java

@@ -156,6 +156,8 @@ public final class AudioDeviceInfo {
 
     /**
      * @return An array of sample rates supported by the audio device.
+     *
+     * Note: an empty array indicates that the device supports arbitrary rates.
      */
     public @NonNull int[] getSampleRates() {
         return mPort.samplingRates();
@@ -166,6 +168,8 @@ public final class AudioDeviceInfo {
      * {@link AudioFormat#CHANNEL_OUT_7POINT1}) for which this audio device can be configured.
      *
      * @see AudioFormat
+     *
+     * Note: an empty array indicates that the device supports arbitrary channel masks.
      */
     public @NonNull int[] getChannelMasks() {
         return mPort.channelMasks();
@@ -175,6 +179,8 @@ public final class AudioDeviceInfo {
      * @return An array of channel index masks for which this audio device can be configured.
      *
      * @see AudioFormat
+     *
+     * Note: an empty array indicates that the device supports arbitrary channel index masks.
      */
     public @NonNull int[] getChannelIndexMasks() {
         return mPort.channelIndexMasks();
@@ -183,6 +189,8 @@ public final class AudioDeviceInfo {
     /**
      * @return An array of channel counts (1, 2, 4, ...) for which this audio device
      * can be configured.
+     *
+     * Note: an empty array indicates that the device supports arbitrary channel counts.
      */
     public @NonNull int[] getChannelCounts() {
         int[] masks = getChannelMasks();
@@ -205,6 +213,8 @@ public final class AudioDeviceInfo {
      * integer precision to that device.
      *
      * @see AudioFormat
+     *
+     * Note: an empty array indicates that the device supports arbitrary encodings.
      */
     public @NonNull int[] getEncodings() {
         return AudioFormat.filterPublicFormats(mPort.formats());